Neuron circuits for a spiking neural network based on magnetic-tunnel-junction layer stacks connected in series

Abstract

Structures including multiple magnetic-tunnel-junction layer stacks and methods of forming such structures. The structure comprises a first magnetic-tunneling-junction layer stack, a second magnetic-tunneling-junction layer stack connected in a series connection to the first magnetic-tunneling-junction layer stack, and a pulsed power supply connected to the first and second magnetic-tunneling-junction layer stacks.

What is claimed is: 
     
         1 . A structure comprising:
 a first magnetic-tunneling-junction layer stack;   a second magnetic-tunneling-junction layer stack connected in a series connection to the first magnetic-tunneling-junction layer stack; and   a pulsed power supply connected to the first magnetic-tunneling-junction layer stack and the second magnetic-tunneling-junction layer stack.   
     
     
         2 . The structure of  claim 1  further comprising:
 an operational amplifier having a first input connected to the first magnetic-tunneling-junction layer stack. 
 
     
     
         3 . The structure of  claim 2  wherein the first magnetic-tunneling-junction layer stack includes an electrode connected to the first input of the operational amplifier, a reference layer, a free layer, and a tunnel barrier layer, and the reference layer is disposed between the electrode and the free layer. 
     
     
         4 . The structure of  claim 3  wherein the first input of the operational amplifier is coupled to the electrode of the first magnetic-tunneling-junction layer stack, and the operational amplifier has a second input connected to ground. 
     
     
         5 . The structure of  claim 1  wherein the first magnetic-tunneling-junction layer stack includes an electrode, and the pulsed power supply is configured to supply a pulsed current to the electrode of the first magnetic-tunneling-junction layer stack. 
     
     
         6 . The structure of  claim 1  further comprising:
 an operational amplifier having an output connected to the second magnetic-tunneling-junction layer stack. 
 
     
     
         7 . The structure of  claim 6  wherein the second magnetic-tunneling-junction layer stack includes an electrode connected to the output of the operational amplifier, a reference layer, a free layer, and a tunnel barrier layer, and the free layer is disposed between the electrode and the reference layer. 
     
     
         8 . The structure of  claim 1  wherein the pulsed power supply is configured to supply a pulsed current to the first magnetic-tunneling-junction layer stack and the second magnetic-tunneling-junction layer stack in the series connection. 
     
     
         9 . The structure of  claim 8  wherein the first magnetic-tunneling-junction layer stack is configured to back-hop in response to the pulsed current and produce a first current spike, and the second magnetic-tunneling-junction layer stack is configured to back-hop in response to the pulsed current and produce a second current spike. 
     
     
         10 . The structure of  claim 9  further comprising:
 a spiking neural network including the first magnetic-tunneling-junction layer stack and the second magnetic-tunneling-junction layer stack. 
 
     
     
         11 . The structure of  claim 10  wherein the first current spike and the second current spike are configured to be additive. 
     
     
         12 . The structure of  claim 11  wherein the first current spike and the second current spike are configured to occur with a probability given by a Poisson probability distribution. 
     
     
         13 . The structure of  claim 1  further comprising:
 a third magnetic-tunneling-junction layer stack connected in the series connection to the first magnetic-tunneling-junction layer stack and the second magnetic-tunneling-junction layer stack. 
 
     
     
         14 . The structure of  claim 13  wherein the first magnetic-tunneling-junction layer stack includes a first electrode, a first reference layer, a first free layer, and a first tunnel barrier layer, and the first free layer is disposed between the first electrode and the first reference layer. 
     
     
         15 . The structure of  claim 14  wherein the third magnetic-tunneling-junction layer stack includes a second electrode connected to the first electrode of the first magnetic-tunneling-junction layer stack, a second reference layer, a second free layer, and a second tunnel barrier layer, and the second reference layer is disposed between the second electrode and the second free layer. 
     
     
         16 . The structure of  claim 13  wherein the third magnetic-tunneling-junction layer stack includes a first electrode, a first reference layer, a first free layer, and a first tunnel barrier layer, and the first free layer is disposed between the first electrode and the first reference layer. 
     
     
         17 . The structure of  claim 16  wherein the second magnetic-tunneling-junction layer stack includes a second electrode connected to the first electrode of the third magnetic-tunneling-junction layer stack, a second reference layer, a second free layer, and a second tunnel barrier layer, and the second reference layer is disposed between the second electrode and the second free layer. 
     
     
         18 . The structure of  claim 1  further comprising:
 a first wiring level including a first interconnect; and 
 a second wiring level including a second interconnect, 
 wherein the first magnetic-tunneling-junction layer stack and the second magnetic-tunneling-junction layer stack are disposed between the first wiring level and the second wiring level. 
 
     
     
         19 . The structure of  claim 18  wherein the first magnetic-tunneling-junction layer stack includes a first electrode that is connected to the first interconnect, the second magnetic-tunneling-junction layer stack includes a second electrode that is connected to the second interconnect, and the first interconnect is connected to the second interconnect. 
     
     
         20 . A method comprising:
 forming a first magnetic-tunneling-junction layer stack; and   forming a second magnetic-tunneling-junction layer stack connected in a series connection to the first magnetic-tunneling-junction layer stack,   wherein the first magnetic-tunneling-junction layer stack and the second magnetic-tunneling-junction layer stack are connected to a pulsed power supply.